A variety of techniques have been developed to test both the waterproofness and breathability of fabrics and articles of clothing. Waterproofness is the capacity of a specimen to keep liquid water from penetrating. One way to test for waterproofness is to fill the test specimen with water and then check for the presence of leaks, or liquid water on the test specimen's outer surface. Breathability is the capacity of a specimen to allow gas to penetrate. When testing a specimen's breathability, the test specimen is typically inflated with gas at a pressure above atmospheric pressure. The test specimen's capacity to allow gas to penetrate is detected by loss of inflation pressure or air bubbles.
One common test of a specimen's waterproofness is to inflate the article and then immerse the inflated article in water. The absence of bubbles escaping from the inflated test specimen is used to demonstrate that the specimen is waterproof. Leaks occur when either a liquid or a gas penetrates a test specimen, whether through the fabric, at the seams, or through material defects. A water leak indicates that the specimen is not waterproof; a gas leak indicates that the test specimen allows gas to penetrate. Thus, the presence of bubbles would indicate that the test specimen has a gas leak.
U.S. Pat. No. 4,799,384 to Casali discloses an apparatus and method for testing for gas leaks in order to demonstrate the waterproofness of footwear articles. In operation, the footwear article is inflated using compressed gas, the top of the article is gripped in such a manner that the gas cannot escape, the article is then immersed in a liquid reservoir which has at least one transparent side. The test article is observed for gas leaks as indicated by the presence of rising bubbles.
U.S. Pat. No. 3,166,439 to Dennhofer discloses an apparatus for examining surgical gloves for gas leaks. Dennhofer pressurizes the gloves with compressed gas while the gloves are under water and inspects for the presence of bubbles.
U.S. Pat. No. 2,054,204 to McDonald also discloses a device wherein surgical gloves can be tested for gas leaks. The sealed glove is placed in a mesh frame to prevent the glove from bulging when pressurized. A small hand pump is used to pressurize the sealed glove, and the pressurized glove within the mesh frame is immersed in a reservoir of water. Bubbles rising from the glove signal the presence of gas leaks.
U.S. Pat. No. 4,776,209 to Patchel discloses a gas leak detector for testing waterproofness wherein a glove or other article may be gas leak tested without getting the article wet. The article is positioned within a testing chamber and both the article and the test chamber are sealed. Gas at a controlled pressure is introduced into the sealed article. A tube fluidly connects the lower end of the test chamber with a reservoir of liquid. If gas leaks from the article into the test chamber, after the initial period of article inflation, then the gas inside the test chamber will exit through the tube into the liquid reservoir, and bubbles will visibly indicate this leakage.
Prior art references thus teach the presence of bubbles as indicative of a gas leak. However, such prior art references use gas pressure greater than ambient to generate bubbles. Furthermore, in such prior art devices a single test may be used to prove that a test specimen is both air tight and waterproof, i.e. if the test specimen does not leak air, it will not leak water.
Also known in the art are techniques for testing a specimen's moisture vapor transmissibility. For instance, U.S. Pat. No. 4,581,921 to Gillespie discloses a moisture vapor transmission test cell, having upper and lower enclosures with a test specimen positioned between the enclosures. Moisture vapor transmissibility is the capacity of a test specimen to allow air and water molecules to penetrate the specimen. Since water molecules are larger than air molecules, there is not an identical correspondence between breathability and moisture vapor transmissibility. A test specimen might let air penetrate, but not let the larger water molecules penetrate.
In Gillespie the upper enclosure contains flowing conditioned air; the lower enclosure contains a fluid/vapor reservoir. During operation, conditioned air flows parallel to the upper surface of a test specimen, while the lower surface of the test specimen is exposed to vapor of a test liquid contained in a reservoir. Vapor is drawn through the test specimen due to the flow of the conditioned air over the surface of the test specimen for a known period of time. At the end of a test cycle, the amount of fluid remaining in the reservoir is a measure of the moisture vapor transmissibility of the test specimen. Gillespie does not test or demonstrate the waterproofness of the test specimen, nor is there any visual display of the test specimen's breathability characteristics.